We will expand our current retrospective cohort study to determine the effect of molecular and histologic factors that affect breast cancer risk in women with non-invasive breast disease. The study cohort will consist of 12,387 women with non-invasive breast disease diagnosed at our study hospitals between 1952 and 1992. Paraffin embedded tissue from their initial breast biopsies is available on these patients. Follow-up to determine breast cancer diagnosis and other epidemiologic risk factors will be obtained or extended through review of hospital and tumor registry records and interviews with these patients or their next-of-kin. We will conduct a series of nested case-control studies on these women. Approximately 615 cohort members will develop invasive breast cancer during 214,990 women-years of follow-up. These women will be our case patients. Two controls will be selected for each case matched on entry histology, age at biopsy and year of biopsy. Our major goals are to determine the influence of various molecular factors on the breast cancer risk associated with different types on benign breast disease. These include abnormal expression or regulation of genes that affect the TGF beta and estrogen signal transduction pathways. We will also study the genes that control estrogen metabolism. PCR and immunohistochemical methods will be used to study gene mutations and abnormal protein expression, respectively. Conditional logistic regression analysis will be used to assess the individual and combined effects of molecular, histologic and epidemiologic variables on breast cancer risk. This project will expand our repository of parafin embedded breast cancer tissue on a large cohort of women with known outcomes. It will permit the combination of modern methods in molecular biology, pathology, and epidemiology to assess potentially powerful new markers of breast cancer prognosis, and may lead to important advances in the prevention and treatment of this disease.